Abstract
PurposeTreatment of sinonasal malignant tumors is challenging, and evidence to establish a standard treatment is limited. Our objective was to evaluate the efficacy and safety of spot scanning proton therapy (SSPT) for sinonasal malignant tumors.Patients and MethodsWe retrospectively analyzed patients with sinonasal malignant tumors (T1-4bN0-2M0) who underwent SSPT between May 2014 and September 2019. The prescription dose was typically either 60 GyRBE in 15 fractions or 60.8 GyRBE in 16 fractions for mucosal melanoma and 70.2 GyRBE in 26 fractions for other histologic subtypes. Endpoints included local control (LC), progression-free survival, overall survival (OS), and incidence of toxicity. Prognostic factors were analyzed using the Kaplan-Meier method and log-rank test.ResultsOf 62 enrolled patients, the common histologic subtypes were mucosal melanoma (35%), squamous cell carcinoma (27%), adenoid cystic carcinoma (16%), and olfactory neuroblastoma (10%). Locally advanced stages were common (T3 in 42% and T4 in 53%). Treatment-naïve tumors and postsurgical recurrent tumors accounted for 73% and 27%, respectively. No patient had previous radiotherapy. The median follow-up was 17 months (range, 6-66) for all patients and 21.5 months (range, 6-66) for survivors. The 2-year LC, progression-free survival, and OS rates of all patients were 92%, 50%, and 76%, respectively. Univariate analysis revealed histology as a prognostic factor for OS, being higher in adenoid cystic carcinoma and olfactory neuroblastoma than in other tumors. Sixteen grade ≥3 late toxicities were observed in 12 patients (19%), including 11 events resulting in visual impairment; the most common was cataract. There was 1 grade 4 toxicity, and there were no grade 5 toxicities.ConclusionSSPT was well tolerated and yielded good LC for sinonasal malignant tumors. Although we consider SSPT to be a leading treatment modality, further studies are required to establish its status as a standard treatment.
Highlights
Sinonasal malignant tumors originating from the nasal cavity and paranasal sinuses are relatively rare, accounting for only about 3% of cancers in the upper respiratory and digestive tract [1]
The present study aimed to investigate the clinical outcomes of spot scanning proton therapy (SSPT) for sinonasal malignant tumors
We found histology to be significantly associated with overall survival (OS); patients with adenoid cystic carcinoma and those with olfactory neuroblastoma had a 2-year OS of 100%
Summary
Sinonasal malignant tumors originating from the nasal cavity and paranasal sinuses are relatively rare, accounting for only about 3% of cancers in the upper respiratory and digestive tract [1]. The appropriate treatment strategy for sinonasal malignant tumors remains controversial, and existing treatment guidelines are supported only by weak clinical evidence [2]. This limited evidence has highlighted the importance of multimodal therapy consisting of surgery, radiation therapy (RT), and systemic therapy [3,4,5]. Proton therapy (PT) is considered an especially promising treatment option. Both planning studies and clinical studies have suggested the superiority of PT over conventional photon therapy, including intensity-modulated radiotherapy [14, 15]
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